Image diagnosis apparatus

ABSTRACT

The image diagnosis apparatus of the present invention is equipped with means for automatically determining a window level and a window width for image displaying in accordance with the value of reconstructed image data. With this window level/window width calculating means (13), the window level is obtained with respect to each reconstructed image on the basis of the virtual average value of its pixel data and the window width is also obtained which has a certain relationship with that window level. When displaying each reconstructed image, a display is made in accordance with each window level and each window width thus obtained. Instead of the obtained window level and window width, those set by a manual setting section (23) may be used by a changeover operation when necessary.

TECHNICAL FIELD

This invention relates to an improvement of an image diagnosis apparatusand more particularly, to an image diagnosis apparatus which is equippedwith means for automatically determining in accordance with the value ofimage data a window level and a window width for image displaying.

BACKGROUND ART

The image diagnosis apparatus, such as NMR imaging apparatus and X-rayCT apparatus, fundamentally comprises data collecting means forcollecting projection data pertaining to a desired section of a subjectto be examined by the use of the nuclear magnetic resonance phenomena orX ray, image reconstructing means for reconstructing the sectional imageof the subject on the basis of the collected projection data, and imagedisplay means for displaying the reconstructed image.

FIG. 9 shows an NMR imaging apparatus which is an example of theforegoing type of image diagnosis apparatus. The NMR imaging apparatushas a magnet section which is configured so that a static magnetic fieldcoil 1 and a gradient magnetic field coil 2 (made up of coils for theindividual x-, y- and z-axes) are disposed in place. The static magneticfield coil 1 is energized by a static magnetic field coil drivingsection 3 with the gradient magnetic field coil 2 by a gradient magneticfield coil driving section 4, so that in the inside space of the magnetthere are created a static magnetic field being uniform in the z-axisdirection and gradient magnetic fields oriented in the same direction asthat of the static magnetic field but each having a linear gradient ineach direction of the x-, y- and z-axes. An exciting coil 5 and adetecting coil 6 are disposed in the magnetic field of the magnetsection while keeping a rotational angle of 90° therebetween about thez-axis, the former coil being energized by an exciting coil drivingsection 7 to apply high-frequency electromagnetic wave pulses to asubject (not shown) placed in the inside space of the magnet with thelatter coil detecting an NMR signal coming from a desired spot of thesubject and applying it to an analog-to-digital converting section(hereinafter referred to as A-D converting section) 8. This A-Dconverting section 8 converts the detection signal into a digital signaland applies it to a control/image processing section 9. Thiscontrol/image processing section 9 is the center of control and imageprocessing over the whole NMR imaging apparatus and is made of acomputer. The control/image processing section 9 is equipped with anexternal memory 10. The control/image processing section 9 controls thestatic magnetic field coil driving section 3, gradient magnetic fieldcoil driving section 4, exciting coil driving section 7 and A-Dconverting section 8 to collect the NMR signal of the subject, andstores the obtained NMR signal (raw data) in the external memory 10.Further, the control/image processing section 9 reconstructs an imagerepresentative of a subject's section on the basis of the raw datastored in the external memory 10 and stores the reconstructed image inthe external memory 10 again. Further, the control/image processingsection 9, in accordance with an instruction from an operator which isgiven through an operator console 15, reads out the reconstructed imagefrom the external memory 10 and applies it through a display controlsection 11 to a display unit 14 where it is displayed. At this stage, awindow level and a window width for image displaying are regulated forthe purpose of making the brightness and gradation of the displayedimage adequate.

In the NMR imaging apparatus, the value of the pixal data forming thereconstructed image and its range of variation, i.e. the brightness andgradation of the reconstructed image, vary depending on the system ofdata collection (pulse sequence), and further, where imaging is carriedout using the multiecho method, since the intensity of each of aplurality of echo signals measured in succession becomes progressivelyweak, the brightness and gradation of each reconstructed image based oneach echo vary. To display several reconstructed images differing inbrightness and gradation in easily-observable form, it is necessary toregulate each window level and window width adequately so that eachimage can be displayed with uniform brightness and gradation. Further,also in other types of image diagnosis apparatus such as X-ray CTapparatus, where the brightness and gradation vary from onereconstructed image to another, the window level and window width mustbe regulated similarly. Hitherto, such a regulation operation for thewindow level and window width was very complicated because it wasperformed by an operator with respect to each reconstructed image.

DISCLOSURE OF THE INVENTION

It is the object of the present invention to provide an image diagnosisapparatus equipped with means for automatically determining inaccordance with the value of reconstructed image data a window level anda window width for image displaying.

The present invention is characterized in that a window level/windowwidth calculating means (13) obtains, with respect to each reconstructedimage, a window level on the basis of the virtual average value of thepixel data of each image and as a window width, a value having a certainrelationship with the value of the window level, and when displayingeach reconstructed image, a display is made in accordance with the thusobtained window level and window width. Instead of the foregoing values,those being set by a manual setting section (23) may be used as thewindow level and window width by a changeover operation when necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing an embodiment of the presentinvention,

FIGS. 2, 3, 5, 6 and 7 are schematic diagrams of the matrix oftwo-dimensional image data pertaining to a reconstructed image,

FIG. 4 is a diagram showing an example of the relationship betweenwindow level and window width,

FIG. 8 is a graph showing an example of the histogram of image datapertaining to a reconstructed image, and

FIG. 9 is a schematic block diagram of an NMR imaging apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of the presentinvention, depicted paying attention to the processing of image data. InFIG. 1, components identical with those of FIG. 9 are designated by thesame reference numerals. The external memory 10 holds raw datapertaining to a subject which has been collected by the NMR imagingapparatus, X-ray CT apparatus, etc. in accordance with the well-knownmethod. The control/image processing section 9 includes a reconstructionprocessing section 12 and a window level/window width calculatingsection (hereinafter referred to as W/L calculating section) 13. Amongthem, the reconstruction processing section 12 processes the raw datastored in the external memory 10 through the known image reconstructiontechnique such as the two-dimensional inverse Fourier transformation andstores the reconstructed image in an image data area of the sameexternal memory 10. The image data thus stored in the external memory 10is read out by the display control section 11 and displayed on thedisplay unit 14. The W/L calculating section 13 obtains, throughtechniques hereinafter described in greater detail and with respect toeach reconstructed image, a window level and a window width used indisplaying each image and stores them in the external memory 10 inpaired form with the image data of the corresponding reconstructedimage. The window level and window width can be set manually by a manualsetting section 23, other than being obtained by the W/L calculatingsection 13. Either the window level and window width stored in theexternal mamory 10 or those set by the manual setting section 23 areselected by a changeover switch 22 to be applied to the display controlsection 11. The changeover switch 22 is turned by controlling an AUT/MANchangeover control section 21. When the display control section 11 is toread out the image data of the external memory 10 and display it on thedisplay unit 14 in the form of an image, a display is made with a windowlevel and a window width which are determined by a window leveldesignating value and a window width designating value given through thechangeover switch 22.

Calculation of the window level and window width is carried out by theW/L calculating section 13 as follows. Let the image data, i.e. thetwo-dimensional image data, pertaining to some reconstructed image begiven in the form of pixel data A(i,j) of N×N matrix as shown in FIG. 2,then, the W/L calculating section 13 obtains the window level L₁ forimage displaying using the pixel data A(i,j) in accordance with thefollowing expression (1): ##EQU1##

This expression (1) means that the average value of the pixel data ofthe reconstructed image is used as the window level. After the windowlevel L₁ is obtained in the foregoing manner, the W/L calculatingsection 13 obtains the window width W₁ using the calculated value L₁ ofthe window level in accordance with the following expression (2):

    W.sub.1 =L.sub.1 to 3L.sub.1                               (2)

That is, the window level L₁ obtained is the average value of all pixeldata, and the window width W₁ obtained is 1 to 3 times the value L₁ ofthe window level. A magnification ratio, 1 to 3, for determination ofthe window width W₁ is determined depending on the type of an objectspot of the subject. These window level L₁ and window width W₁ areannexed to the two-dimensional image data pertaining to thereconstructed image as part of file information and stored in theexternal memory 10. Then, when making an image display with thechangeover switch 22 turned to the AUT side, the two-dimensional imagedata and the window level L₁ and window width W₁ annexed to that dataare read out and applied to the display control section 11, so that adisplay is made with the intermediate value of the brightness of thedisplay image, i.e. the window level, being set to the average value ofthe pixels and with the difference between the white level and the blacklevel, i.e. the window width, being set to 1 to 3 times the averagevalue of the pixel data. Accordingly, irrespective of what range thevalue of the pixel data of the reconstructed image falls within, itsaverage value is always taken as the window level and this average valuemultiplied by a certain factor as the window width to display an image,so that any image can be displayed with uniform brightness andgradation. Where the changeover switch 22 has been turned to the MANside, similarly to the prior art, an image display is made on the basisof a desired window level and a desired window width corresponding tothe setting values of the manual setting section 23.

Determination of the window level and window width done by the W/Lcalculating section 13 can be carried out in accordance with, other thanthe foregoing expressions (1) and (2), several manners as follows. Thatis,

(a) As shown in FIG. 3, the average value of the M×M pixels locatedinside a limited central area out of the matrix of the two-dimensionalimage data is taken as the window level L₂, and 1 to 3 times the windowlevel L₂ is taken as the window width W₂.

(b) As shown in FIG. 4, 0.5 to 1 times the difference between themaximum value L_(max) =A_(ij)(max) and the minimum value L_(min)=A_(ij)(min) of all pixel data of the two-dimensional image data istaken as the window width W₃, and the intermediate value of them istaken as the window level L₃.

(c) As shown in FIG. 5, 0.5 to 1 times the difference between themaximum value L_(max) =B_(ij)(max) and the minimum value L_(min)=B_(ij)(min) out of the individual average values of the pixel data ofsub-areas, n×n, of the matrix of the two-dimensional image data is takenas the window width W₄, and the intermediate value of them is taken asthe window level L₄.

(d) As shown in FIG. 6, 0.5 to 1 times the difference between themaximum value and the minimum value of the pixel data of a specifiedvertical or horizontal band-like area in the matrix of thetwo-dimensional image data is taken as the window width W₅, and theintermediate value of them is taken as the window level L₅.

(e) As shown in FIG. 7, the average value of the inside pixel data ofthe inscribed circle of the matrix of the two-dimensional image data istaken as the window level L₆, and 2 times the difference between thataverage value and the average value of the outside pixel data of thesame is taken as the window width W₆.

(f) As shown in FIG. 8, the center of gravity of the histogram of allpixel data of the two-dimensional image data, which is calculated inaccordance with the following expression (3): ##EQU2## , is taken as thewindow level L₇, and 1 to 3 times the L₇ is taken as the window widthW₇.

(g) One out of the foregoing window levels L₁ through L₇ and one out ofthe foregoing window widths W₁ through W₇ are selected to provide acombination of them that differs from the foregoing.

It should be noted that the switching between AUT and MAN done by thechangeover switch 22 may be made independently between the window leveland the window width. In this case, the calculated value held in theexternal memory 10 of either the window level or the window width isused as the one, and some value manually set in the manual settingsection is used as the other.

Although the best mode for embodying the present invention has beendescribed, it is easy for those skilled in the art to make variouschanges without departing from the scope of the appended claims.

What is claimed is:
 1. In an image diagnosis apparatus comprisingmeansfor collecting data pertaining to tissue configuration or biochemicalfunctions of a subject to be examined; means for converting said datainto two-dimensional image data by reconstruction processing; means forstoring said two-dimensional image data in a memory means; means formanually setting a window level and a window width; and means forgenerating an image based on said two-dimensional image data; theimprovement comprising calculating means for calculating a window leveland a window width peculiar to each two-dimensional image data inaccordance with a predetermined calculation method; memory means forstoring the values calculated by said calculating means in annexed formto each two dimensional image data; and switching means for selectivelyswitching to said means for generating an image any of the following:(1)said set window level and said set window width, (2) said calculatedwindow level and said calculated window width, (3) said set window leveland said calculated window width, or (4) said calculated window leveland said set window width.
 2. In an image diagnosis apparatuscomprisingmeans for collecting data pertaining to tissue configurationor biochemical functions of a subject to be examined; means forconverting said data into two-dimensional image data by reconstructionprocessing; means for storing said two-dimensional image data in amemory means; means for manually setting a window level and a windowwidth; and means for generating an image based on said two-dimensionalimage data; the improvement comprising calculating means for calculatinga window level and a window width peculiar to each two-dimensional imagedata in accordance with a predetermined calculation method; memory meansfor storing the values calculated by said calculating means in annexedform to each two dimensional image data; and switching means forselectively switching said set window level and said window width orsaid calculated window level and said calculated window width, or anycombination thereof, to said means for generating an image; wherein saidcalculating means calculates a window level by taking the average valueof all pixels of an image to be reconstructed, and calculates a windowwidth by multiplying the calculated window level by a factor of 1 to 3.3. In an image diagnosis apparatus comprisingmeans for collecting datapertaining to tissue configuration or biochemical functions of a subjectto be examined; means for converting said data into two-dimensionalimage data by reconstruction; means for storing said two-dimensionalimage data in a memory means; means for manually setting a window leveland a window width; and means for generating an image based on saidtwo-dimensional image data; the improvement comprising calculating meansfor calculating a window level and a window width peculiar to eachtwo-dimensional image data in accordance with a predeterminedcalculation method; memory means for storing the values calculated bysaid calculating means in annexed form to each two dimensional imagedata; and switching means for selectively switching said set windowlevel and said set window width or said calculated window level and saidcalculated window width, or any combination thereof, to said means forgenerating an image; wherein said calculating means calculates a windowlevel by taking the average value of pixels in a limited central area ofan image to be reconstructed, and calculates a window width bymultiplying the calculated window level by a factor of 1 to
 3. 4. In animage diagnosis apparatus comprisingmeans for collecting data pertainingto tissue configuration or biochemical functions of a subject to beexamined; means for converting said data into two-dimensional image databy reconstruction processing; means for storing said two-dimensionalimage data in a memory means; means for manually setting a window leveland a window width; and means for generating an image based on saidtwo-dimensional image data; the improvement comprising calculating meansfor calculating a window level and a window width peculiar to eachtwo-dimensional image data in accordance with a predeterminedcalculation method; memory means for storing the values calculated bysaid calculating means in annexed form to each two-dimensional imagedata; and switching means for selectively switching said set windowlevel and said set window width or said calculated window level and saidcalculated window width, or any combination thereof, to said means forgenerating an image; wherein said calculating means calculates a windowlevel by taking an intermediate value between the maximum value and theminimum value of all pixels of an image to be reconstructed, andcalculates a window width by multiplying the difference between the lastmentioned said maximum and minimum values by a factor of 0.5 to
 1. 5. Inan image diagnosis apparatus comprisingmeans for collecting datapertaining to tissue configuration or biochemical functions of a subjectto be examined; means for converting said data into two-dimensionalimage data by reconstruction processing; means for storing saidtwo-dimensional image data in a memory means; means for manually settinga window level and a window width; and means for generating an imagebased on said two-dimensional image data; the improvement comprisingcalculating means for calculating a window level and a window widthpeculiar to each two-dimensional image data in accordance with apredetermined calculation method; memory means for storing the valuescalculated by said calculating means in annexed form to eachtwo-dimensional image data; and switching means for selectivelyswitching said set window level and said set window width or saidcalculated window level and said calculated window width, or anycombination thereof, to said means for generating an image; wherein saidcalculating means calculates a window level by taking an intermediatevalue between the maximum value and the minimum value of individualaverage values of sub-areas defined on pixels of an image to bereconstructed, and calculates a window width by multiplying thedifference between the last mentioned said maximum and minimum values bya factor of 0.5 to
 1. 6. In an image diagnosis apparatus comprisingmeansfor collecting data pertaining to tissue configuration or biochemicalfunctions of a subject to be examined; means for converting said datainto two-dimensional image data by reconstruction processing; means forstoring said two-dimensional image data in a memory means; means formanually setting a window level and a window width; and means forgenerating an image based on said two-dimensional image data; theimprovement comprising calculating means for calculating a window leveland a window width peculiar to each two-dimensional image data inaccordance with a predetermined calculation method; memory means forstoring the values calculated by said calculating means in annexed formto each two-dimensional image data; and switching means for selectivelyswitching said set window level and said set window width or saidcalculated window level and said calculated window width, or anycombination thereof, to said means for generating an image; wherein saidcalculating means calculates a window level by taking an intermediatevalue between the maximum value and the minimum value of pixels locatedinside a limited vertical or horizontal band-like area of an image to bereconstructed, and calculates a window width by multiplying thedifference between the last mentioned said maximum and minimum values bya factor of 0.5 to
 1. 7. In an image diagnosis apparatus comprisingmeansfor collecting data pertaining to tissue configuration or biochemicalfunctions of a subject to be examined; means for converting said datainto two-dimensional image data by reconstruction processing; means forstoring said two-dimensional image data in a memory means; means formanually setting a window level and a window width; and means forgenerating an image based on said two-dimensional image data; theimprovement comprising calculating means for calculating a window leveland a window width peculiar to each two-dimensional image data inaccordance with a predetermined calculation method; memory means forstoring the values calculated by said calculating means in annexed formto each two-dimensional image data; and switching means for selectivelyswitching said set window level and said set window width or saidcalculated window level and said calculated window width, or anycombination thereof, to said means for generating an image; wherein saidcalculating means calculates a window level by taking the average valueof pixels located inside an inscribed circle of an image to bereconstructed, and calculates a window width by multiplying thedifference between said last mentioned average value and the averagevalue of pixels located outside said inscribed circle by a factor of 2.8. In an image diagnosis apparatus comprisingmeans for collecting datapertaining to tissue configuration or biochemical functions of a subjectto be examined; means for converting said data into two-dimensionalimage data by reconstruction processing; means for storing saidtwo-dimensional image data in a memory means; means for manually settinga window level and a window width; and means for generating an imagebased on said two-dimensional image data; the improvement comprisingcalculating means for calculating a window level and a window widthpeculiar to each two-dimensional image data in accordnace with apredetermined calculation method; memory means for storing the valuescalculated by said calculating means in annexed form in eachtwo-dimensional image data; and switching means for selectivelyswitching said set window level and said set window width or saidcalculated window level and said calculated window width, or anycombination thereof, to said means for generating an image; wherein saidcalculating means calculates a window level by taking the center ofgravity of a histogram of all pixels of an image to be reconstructed,and calculates a window width by multiplying said calculated windowlevel by a factor of 1 to
 3. 9. The apparatus of claim 2, 3, 4, 5, 6, 7or 8, wherein said means for generating an image generates an imagedisplay based on a two-dimensional data using one of the calculatedwindow levels, and a set window width.
 10. The apparatus of claim 2, 3,4, 5, 6, 7 or 8, wherein said means for generating an image generates animage display based on a two-dimensional data using one of thecalculated window widths, and a set window level.
 11. In an imagediagnosis apparatus comprisingmeans for collecting data pertaining totissue configurations or biochemical functions of a subject beingexamined; means for storing two-dimensional image data in a memorymeans; means for calculating window level and window width; and meansfor generating an image based on said two-dimensional image data andusing the calculated window level and window width; the improvementwherein said means for calculating calculates a window level by takingthe average value of all pixels of a predetermined area of an image tobe reconstructed, and calculates a window width by multiplying thecalculated window level by a predetermined factor.
 12. The apparatus ofclaim 11, wherein said calculating means calculates a window level bytaking the average value of all pixels of an image to be reconstructed,and calculates a window width by multiplying the calculated window levelby a factor of 1 to
 3. 13. The apparatus of claim 11, wherein saidcalculating means calculates a window level by taking the average valueof pixels in a limited central area of an image to be reconstructed, andcalculates a window width by multiplying the calculated window level bya factor of 1 to
 3. 14. The apparatus of claim 11, wherein saidcalculating means calculates a window level by taking an intermediatevalue between the maximum value and the minimum value of all pixels ofthe predetermined area of an image to be reconstructed, and calculates awindow width by multiplying the difference between the last mentionedsaid maximum and minimum values by a factor of 0.5 to
 1. 15. Theapparatus of claim 11, wherein said calculating means calculates awindow level by taking an intermediate value between the maximum valueand the minimum value of individual average values of sub-areas definedon pixels of the predetermined area of an image to be reconstructed, andcalculates a window width by multiplying the difference between the lastmentioned said maximum and minimum values by a factor of 0.5 to
 1. 16.The apparatus of claim 11, wherein said calculating means calculates awindow level by taking an intermediate value between the maximum valueand the minimum value of pixels located inside a limited vertical orhorizontal band-like area of the predetermined area of an image to bereconstructed, and calculates a window width by multiplying thedifference between the last mentioned said maximum and minimum values bya factor of 0.5 to
 1. 17. The apparatus of claim 11, wherein saidcalculating means calculates a window level by taking the average valueof pixels located inside an inscribed circle of an image to bereconstructed, and calculates a window width by multiplying thedifference between said last mentioned average value and the averagevalue of pixels located outside said inscribed circle by a factor of 2.18. The apparatus of claim 11, wherein said calculating means calculatesa window level by taking the center of gravity of a histogram of allpixels of the predetermined area of an image to be reconstructed, andcalculates a window width by multiplying said calculated window level bya factor of 1 to
 3. 19. The apparatus of claim 12, 13, 14, 15, 16, 17 or18, wherein said means for generating an image generates an imagedisplay based on a two-dimensional data using one of the calculatedwindow levels.
 20. The apparatus of claim 12, 13, 14, 15, 16, 17 or 18,wherein said means for generating an image generates an image displaybased on a two-dimensional data using one of the calculated windowwidths.
 21. In an image diagnosis apparatus comprisingmeans forcollecting data pertaining to tissue configurations or biochemicalfunctions of a subject to be examined; means for storing two-dimensionalimage data in a memory means; means for calculating window level andwindow width; and means for generating an image based on saidtwo-dimensional image data and using the calculated window level andwindow width; the improvement wherein said means for calculatingcalculates a window level by taking an intermediate value between themaximum value and the minimum value of all pixels of a predeterminedarea of an image to be reconstructed, and calculates a window width bymultiplying the difference between the last mentioned said maximum andminimum values by a factor of 0.5 to
 1. 22. The apparatus of claim 21,wherein said calculating means calculates a window level by taking anintermediate value between maximum and minimum values of individualaverage values of sub-areas defined on pixels of an image to bereconstructed.
 23. The apparatus of claim 21, wherein said calculatingmeans calculates a window level by taking the intermediate value betweenthe maximum and minimum values of pixels located inside a limitedvertical or horizontal band-like area of an image to be reconstructed.